1. Field of the Invention
The present invention relates to a photo development apparatus and a method for fabricating a display panel using the same, and more particularly, to a photo development apparatus and a method for fabricating a color filter substrate for a display panel using the same.
2. Description of the Related Arts
A liquid crystal display device controls the light transmissivity of liquid crystal, which has dielectric anisotropy, by the use of an electric field, thereby displaying a picture. For this, the liquid crystal display device includes a liquid crystal display panel to display a picture through a liquid crystal cell matrix and a drive circuit to drive the liquid crystal display panel.
As shown in FIG. 1, a liquid crystal display panel of the related art includes a color filter substrate 10 and a thin film transistor substrate 20 which are bonded together with liquid crystal 24 therebetween.
The color filter substrate 10 includes a black matrix 4, a color filter 6 and a common electrode 8, which are sequentially formed on an upper glass substrate 2. The black matrix 4 is formed on the upper glass substrate in a matrix shape. The black matrix 4 divides the area of the upper glass substrate 2 into a plurality of cell areas in which a color filter is to be formed, and prevents the optical interference and external light reflection between the adjacent cells. The color filter 6 is formed to be divided into red R, green G, blue B in the cell area divided by the black matrix 4 to transmit red, green and blue lights, respectively. The transparent common electrode 8, which spreads over the entire surface of the color filter 6, supplies a common voltage Vcom as a reference voltage for driving the liquid crystal 24. In addition, to flatten the color filter 6, an overcoat layer (not shown) is formed between the color filter 6 and the common electrode 8.
The thin film transistor substrate 20 includes a thin film transistor 18 and a pixel electrode 22, wherein the thin film transistor 18 is formed in every cell area which is defined by the intersection of a gate line 14 and a data line 16 on a lower glass substrate 12. The thin film transistor 18 supplies a data signal from the data line 16 to the pixel electrode 22 in response to a gate signal from the gate line 14. The pixel electrode 22 formed of a transparent conductive layer supplies the data voltage from the thin film transistor 18 to drive the liquid crystal 24.
The liquid crystal 24 having a dielectric anisotropy rotates along the electric field formed by the common voltage Vcom of the common electrode 8 and the data voltage of the pixel electrode 22 to control the light transmissivity, thereby creating a corresponding gray level image.
The liquid crystal display panel further includes a spacer (not shown) to maintain a fixed cell gap between the color filter substrate 10 and the thin film transistor substrate 20. The spacer is a ball spacer or a column spacer. The column spacer is mainly used for a large sized liquid crystal display panel. The column spacer is mainly used in a method of forming liquid crystal by a drop-filling and is mainly formed on the overcoat layer that covers the color filter.
The color filter substrate 10 and the thin film transistor substrate 20 of the liquid crystal display panel are formed by use of a plurality of mask processes. One fabrication method includes a plurality of processes such as a thin film deposition (coating) process, a cleaning process, a photolithography process (hereinafter, referred to as a “photo process”), an etching process, a photo-resist peeling process, an inspection process and so on.
The photo process progresses in the order of coating a photo-resist, exposure, development, and firing. Here, the photo-resist has a photo sensitivity and can be patterned by the exposure process. The photo-resist is classified as a positive type or a negative type in accordance with its characteristics. The positive photo-resist and the negative photo-resist should each be developed with different development solutions. Generally, the positive photo-resist is a resin of Novolak type, and a TMAH development solution is used. The negative photo-resist is a resin of acrylic type, and a KOH development solution is used. If these two development solutions are mixed even in a small amount, the photo-resist phenomenon is not generated properly. Thus, there is a problem in that the two types of photo-resists cannot be used in one photo apparatus at the same time.
In other words, in the event that both the positive photo-resist and the negative photo-resist are to be used, separate photo apparatuses are needed for processing the positive photo-resist and processing the negative photo-resist. Further, a development solution supply apparatus which supplies development solutions to each photo apparatus should also include separate apparatuses for supplying a positive development solution and supplying a negative development solution.
For example, in the color filter substrate, a positive photo-resist is used for the black matrix and a negative photo-resist is used for the color filters. Further, a negative photo-resist is used for the overcoat layer and the column spacer. A negative photo-resist is also used for the resin black matrix which is mainly used for a horizontal electric field application type of liquid crystal display panel. Accordingly, there is a disadvantage in that the equipment operation rate decreases when operating a backup apparatus because a positive photo apparatus and a negative photo apparatus are separately needed, and the positive development solution supply apparatus and the negative development solution supply apparatus are separately needed to form the color filter substrate. The fabricating apparatus and method for the color filter substrate of the related art are explained with reference to FIGS. 2 and 3.
FIG. 2 is a block diagram illustrating a photo development apparatus used in fabricating a color filter substrate according to the related art. FIG. 3 is a diagram illustrating, step by step, a related art process of forming the color filter substrate with the use of the fabricating apparatus shown in FIG. 2.
The photo development apparatus of the color filter substrate shown in FIG. 3 includes a BM photo apparatus 62 to form the black matrix, and R, G, and B photo apparatuses 64, 66, and 68 to form R, G, and B color filters, respectively. The photo development apparatus also includes a first development solution supplier 70 to supply a positive development solution to the BM photo apparatus 62, and a second development solution supplier 72 to supply a negative development solution to the R, G, and B photo apparatuses 64, 66, and 68.
As shown in FIG. 3, in the first step S1, a Cr layer 32 is formed on an upper glass substrate by a separate deposition apparatus (not shown). In the second step S2, a BM photo apparatus 62 forms a photo-resist pattern 34 on the Cr layer 32 by a photo process using a first mask. The BM photo apparatus 62 coats a positive photo-resist on the Cr layer 32 and exposes it through a first mask, and then it develops the positive photo-resist using the positive development solution from the first development solution supplier 70, thereby forming a photo-resist pattern 34. In the third step S3, a separate etching apparatus (not shown) etches the Cr layer 32 by an etching process using the photo-resist pattern 34 as a mask to form a black matrix 40. Then, a strip apparatus (not shown) removes the photo-resist pattern 34 left on the black matrix 40.
In the fourth step S4, the R photo apparatus 64 forms an R color filter in a corresponding pixel area of a substrate 30 where the black matrix 40 is formed. The R photo apparatus 64 coats an R photo-resist having an R pigment on the substrate 30 where the black matrix 40 is formed and exposes it. The R photo apparatus 64 then develops the R photo-resist by using the negative development solution from the second development supplier 72, thereby forming the R color filter.
In the fifth step S5, the G photo apparatus 66 forms a G color filter in a corresponding pixel area by the same photo process as in step S4, and in the sixth step S6, the B photo apparatus 68 forms a B color filter in a corresponding pixel area by the same photo process.
In the seventh step S7, a common electrode deposition apparatus (not shown) forms a common electrode 42 which covers the R, G, B color filter.
In the event that the color filter substrate having a resin black matrix is fabricated with the use of the related art photo development apparatus, because the BM photo apparatus 62 of the positive type shown in FIG. 2 cannot be used for the negative type, the BM photo apparatus of the negative type is separately provided. However, the BM photo apparatuses of the positive type and of negative type need to stop operating from time to time to make their production quantity match that of the R, G, and B photo apparatus 64, 66, and 68. Accordingly, there is a problem in that the operation rate of two BM photo apparatuses decreases by 50% so that their productivity decreases.
Further, with respect to providing a backup photo apparatus for improving productivity, a backup apparatus of the positive type and a backup apparatus of the negative type are separately needed. For example, a method may utilize one backup BM photo apparatus of the positive type and one backup color photo apparatus of the negative type to produce the R, G, and B color filters in a sequential manner in order to use a minimum number of backup apparatuses. In this case, however, while the BM photo backup apparatus is used to form the black matrix, the color photo backup apparatus should form the R, G, and B color filters. Thus, the production imbalance between the backup apparatuses is created so that the productivity increases by only one third of the basic photo development apparatus production.